Armour-piercing fin-stabilized discarding sabottracer or APFSDS-T rounds. Typically used against other modern tanks.

There are different ways to measure penetration value. NATO uses the 50% (This means that 50% of the shell had to go through the plate), while the Soviet/Russia standard is higher (80% had to go through). According to authorities like Paul Lakowski, the difference in performance can reach as much as 8%[1]

Entered service in 2014. Uses the 3VM-18 programmable detonator. The projectile contained 450 tungsten rod every weight 3 gram and creates 2,500 fragments when air burst mode set.Air burst mode for use against infantry,light vehicles and helicopters, delayed mode use against bunkers and other constructions.

Use for 2A82-1M gun on T-14s, has Millimeter waveSACLOS guidance and a tandem shaped-charge HEAT warhead. It has an effective range of 50 m to 8000 m.It can penetrate 950 millimetres (37 in) of steel armour after Explosive Reactive Armor and can also engage low-flying air targets such as helicopters.

1.
2A46 125 mm gun
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The 2A46 is a 125mm/L48 smoothbore cannon of Soviet origin used in several main battle tanks. It was designed by OKB-9 in Sverdlovsk and it was developed by the Spetstekhnika Design Bureau in Ekaterinburg in the 1960s originally for the T-64A tank. They were subsequently manufactured at Artillery Plant No.9 in Ekaterinburg, versions include 2A46, 2A46M, 2A46M-1, 2A46M-2, 2A46M-4, 2A46M-5 and the Ukrainian KBA-3. The 2A46 can fire armour-piercing fin-stabilised discarding sabot, high-explosive anti-tank, the ammunition for the 2A46 gun is in two pieces, the projectile is loaded first, followed by a separate propellant charge. The early version of the 2A46 suffered from a barrel life. The Ukrainian KBA guns are derived from the 2A46 gun, the 2A46 has been used in numerous tanks, almost exclusively Soviet/Russian designs or foreign derivatives thereof. armor. kiev. ua/

2.
T-64
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The T-64 is a Soviet second-generation main battle tank introduced in the early 1960s. It was a more advanced counterpart to the T-62, the T-64 served tank divisions, in spite of being armed and armored like a heavy tank, the T-64 weighed only 38 tonnes. These features made the T-64 expensive to build, significantly higher than previous generations of Soviet tanks and this was especially true of the power pack. Several proposals were made to improve the T-64 with new engines and this led to the T-72 being designed as an emergency design, only to be produced in the case of a war, but its 40% lower price led to it entering production in spite of Morozovs objections. Although the T-62 and the famous T-72 would see much use and generally more development, it was the T-64 that formed the basis of subsequent modern Soviet tank designs. The T-64 was conceived in Kharkiv, Ukraine, as the main battle tank by Alexander A. Morozov. The T-64 design was developed by LKZ as the gas turbine-powered T-80 main battle tank. The turret of the T-64B would be used in the improved T-80U and T-80UD, the T-64 would only be used by the Soviet Army and never exported, unlike the T-54/55. By 1981, the improved T-64B began to be deployed in East Germany, while it was believed that the T-64 was only reserved for elite units, it was also used by much lower non-ready formations, for example, the Odessa Military Districts 14th Army. With the break-up of the Soviet Union in 1991, T-64 tanks remained in the arsenals of Russia, Ukraine, Belarus and Uzbekistan. Mid 2014, slightly fewer than 2,000 of the former Soviet inventory of T-64 tanks are in service with the military of Ukraine and about 4,000 are out-of-service, for the first time in the world. It has autoloader with a choice of shells, Armor received composite additives, previously all tanks had only metal. More than 1100 T-64 tanks were produced between 1964 and 1968, it was Object 432, the combat rate of fire reached 10 rounds per minute. In the first years of development the tank was invulnerable, opponents of the tank can be destroyed by shooting at the forehead from a distance of 1. 5-2km. Turret almost all closed reactive protection, the case is closed on the sides of the forehead, in the early 70s, heat ammunition can not penetrate reactive protection in most cases. Studies for the design of a new battle tank started as early as 1951, a project named obyekt 430 gave birth to three prototypes, which were tested in Kubinka in 1958. Those vehicles showed characteristics that were going to change the design of battle tanks on this side of the Iron Curtain. For the first time, an extremely compact opposed-piston engine was used, the transmission system comprised two lateral gears on each side of the engine

3.
T-72
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The T-72 is a Soviet second-generation main battle tank that entered production in 1971. About 20,000 T-72 tanks were built, making it one of the most widely produced post–World War II tanks, the T-72 was widely exported and saw service in 40 countries and in numerous conflicts. The development of the T-72 was a result of the introduction of the T-64 tank. The T-64 was an ambitious project to build a competitive tank with a weight of not more than 36 tons under the direction of Alexander Morozov in Kharkov. To achieve that goal, the crew was reduced to three soldiers, saving the loader by introducing an automated loading system and this and other steps allowed a reduced weight, but caused problems when looking for a reliable engine to fit in the smaller hull. The production of the T-64 with a 115-mm gun began in 1964, problems with the first batch of T-64 tanks were centred on the 5TDF700 hp engine and the auto loading mechanism. The engine was unreliable, was difficult to repair and had a life span of only a World War 2-era tank engine. A strong lobby around designer Morozov advocated for the T-64 in Moscow, preventing rival developments, the 5TDF was too complex and its production twice as costly as the V-45 engine. In 1967, the Uralvagonzavod formed Section 520, which was to prepare the serial production of the T-64 for 1970. The team soon found out that the more powerful V-45 engine put a lot of stress on the fragile T-64 hull, a more stable solution had to be found. Under influence from Kharkov, the idea had been turned down by Moscow, but this construction, with its big, rubbercoated roadwheels now formed the basis for the mobilisation model of the T-64. Additional changes were made to the loading system, which also was taken from an earlier project. Ammunition, consisting of a projectile and a propellant charge was now stored horizontally on two levels, not vertically on one level like in the T-64. It was said to be more reliable than the T-64 autoloader, in 1964, two 125-mm guns of the D-81 type had been used to test their installation in the T-62, so the Ural plant was ready to adopt the 125-mm calibre for the T-64A as well. Uralvagonzavod produced the first prototype with a 125-mm gun and V-45K engine in 1968 as Object 172, after intensive comparative testing with the T-64A, Object 172 was re-engineered in 1970 to deal with some minor problems. However, being only a model, a serial production of Object 172 was not possible in peacetime. In an unclear political process decree number 326-113 was issued, which allowed the production of Object 172 in the Soviet Union from 1, January 1972 and freed Uralvagonzavod from the T-64A production. At least some technical documentation on the T-72 is known to have passed to the CIA by the Polish Colonel Ryszard Kuklinski between 1971 and 1982

4.
T-80
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The T-80 is a third-generation main battle tank designed and manufactured in the Soviet Union. When it entered service in 1976, it was the first MBT in the world to feature a powerful multifuel turbine engine as its main propulsion engine. The T-80U was last produced in a factory in Omsk, Russia, while the T-80UD, the T-80 and its variants are in service in Belarus, Cyprus, Egypt, Kazakhstan, Pakistan, Russia, South Korea, and Ukraine. The chief designer of the T-80 was the Russian engineer Nikolay Popov, the project to build the first Soviet turbine powered tank began in 1949. Its designer was A. Ch. Starostienko, who worked at the Leningrad Kirov Plant, the tank was never built because available turbine engines were of very poor quality. In 1955 two prototype 1,000 hp turbine engines were built at the plant under the guidance of G. A. Ogloblin. Two years later a team led by the heavy tank designer Josef Kotin constructed two prototypes of the Obyekt 278 tank. Both were hybrids of the IS-7 and the T-10 heavy tanks, powered by the GTD-1 turbine engine, weighing 53.5 tonnes and armed with the M65130 mm tank gun. The turbine engine allowed the tank to reach a speed of 57.3 km/h but with only 1950 liters of fuel on board. The two tanks were considered experimental vehicles and work on them eventually ceased, in 1963, the Morozov Design Bureau designed the T-64 and T-64T tanks. They used a GTD-3TL turbine engine which generated 700 hp, the tank was tested until 1965. At the same time at Uralvagonzavod a design team under the guidance of L. N. Kartsev created the Obyekt 167T tank and it used the GTD-3T turbine engine which supplied 801 hp. In 1966 the experimental Obyekt 288 rocket tank, powered by two aerial GTD-350 turbine engines with a power of 691 hp, was first built. Trials indicated that propulsion was no better than the turbine engine which had been in development since 1968 at KB-3 of the Kirov Plant. The tank from LKZ equipped with this engine was designed by Nikolay Popov. It was constructed in 1969 and designated Obyekt 219 SP1 and it was renamed the T-64T, and was powered by a GTD-1000T multi-fuel gas turbine engine producing up to 1,000 hp. During the trials it became clear that the weight and dynamic characteristics required a complete redesign of the vehicles caterpillar track system. The second prototype, designated Obyekt 219 SP2, received bigger drive sprockets, the number of wheels was increased from five to six

5.
M-84
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The M-84 is a Yugoslav third generation main battle tank, a variant of the Soviet T-72. The M-84 is still in service in Serbia, Kuwait, Croatia, and Slovenia, the M-84 is based on the Soviet T-72 but with several modifications, including a domestic fire-control system, improved composite armor, and a 1000-hp engine. The M-84 entered service with the Yugoslav Peoples Army in 1984, the improved M-84A version entered service a few years later. There were about 240 Yugoslav factories which directly participated in the production of the M-84, the main factories were, The latest Serbian version of the M-84 is the M-84AS, unveiled in 2004. It features a new control system, Kontakt-5 ERA armor, AT-11 Sniper anti-tank missiles, Agava-2 thermal sight. It is very similar to the Russian T-90S, both in appearance and in capability, about 150 M-84 tanks were exported to Kuwait. The disintegration of Yugoslavia in the 1990s prevented further exports of the M-84, the M-84A is armed with a 125 mm smooth bore cannon. The M-84 uses an automatic loader, which enables it to sustain a rate of 8 rounds per minute. The cannons ammunition is stowed underneath the turret within the hull of the tank and this concept was inherited from the original Soviet design for T-72 and is both a strength and weakness of the tank. This weakness was exploited by Croatian soldiers in the Croatian War of Independence to the detriment of the Yugoslav Peoples Armys tank crews, in later stages of the conflict, losses were reduced by adjusting and improving tactics. Along with its armament, the M-84 is also armed with one 7. 62mm coaxial machine gun. All versions of the M-84 have a crew of three, the commander sits on the right side of the turret, the gunner on the left, and the driver sits centrally at the front end of the vehicle. Like most Soviet derived vehicles, the M-84 series of tanks do not have a manual loader, the glacis uses laminate armor, glass in plastic resin between two steel plates, in the A version a 16mm steel plate was welded on the glacis. Total armor protection ranges between 550mm-650mm for the glacis and 560mm-700mm for the turret, during the wars in Yugoslavia the M-84s frontal armor proved very effective against any type of AT threat. Side or rear hits often result in a catastrophic ammo explosion, twelve smoke grenades are positioned in front of the turret in banks of five and seven grenades. Night vision and gunners sight are positioned on the side of the turret. The M-84 has a search light used in combat situations. The M-84 tank has nuclear, biological and chemical protection capabilities, the base M-84 engine is a 12-cylinder water-cooled V46-6 diesel engine, rated at 574 kW

6.
T-90
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The T-90 is a third-generation Russian battle tank that entered service in 1993. The tank is a variation of the T-72B and incorporates many features found on the T-80U. Originally called the T-72BU, but later renamed to T-90, it is a tank in service with Russian Ground Forces. The T-90 uses a 125mm 2A46 smoothbore main gun, the 1A45T fire-control system, an uprated engine, standard protective measures include a blend of steel and composite armour, smoke grenade dischargers, Kontakt-5 explosive-reactive armour and the Shtora infrared ATGM jamming system. It was designed and built by Uralvagonzavod, in Nizhny Tagil, since 2011, the Russian armed forces have ceased any further orders for the T-90, and are instead anticipating the development of the T-14 Armata that is expected to enter service in 2016. The T-90 has its origins in a Soviet-era program aimed at developing a replacement for the T-64, T-72. The T-72 platform was selected as the basis for the new generation of tank owing to its cost-effectiveness, simplicity, development work was approved in 1986 and the first prototypes were completed by 1988. The vehicles resulting from the Object 187 program have not been declassified to this date, less than 200 T-90 tanks were delivered to the Russian Ground Forces before production was resumed in 2005 of an upgraded version. By September 1995, some 107 T-90 tanks had been produced, located in the Siberian Military District. The first 42 complete Indian tanks were delivered in 2001 and were designated T-90S, still equipped with the older cast turrets of the early series and powered by the V-84 engine making 840hp. This was followed up next year with delivery of 82 vehicles, now equipped with the new welded turrets, in 2005 the Russian army resumed delivery of the T-90, requesting the original specification for the vehicle with a cast turret. That same year saw delivery of an additional 18 new tanks - enough to one whole battalion. These new Russian tanks were powered by the V-92S2 engine, carried a T01-K05 Buran-M gunners sight and were protected by the most recent Kontakt-5 reactive armor with 4S22 explosive tiles, since 2008, the Russian army has received 62 tanks annually, suspending orders in 2011. Russia is developing the new Armata Universal Combat Platform to be ready for use by 2016 and it is expected to employ a more powerful engine, improved armor, main gun and autoloader, with ammunition storage separated from the crew. An early variant of the export-oriented T-90S allegedly saw combat action during the 1999 Chechen invasion of Dagestan instead of being delivered to India, according to Moscow Defence Brief, one vehicle was hit by seven RPG anti-tank rockets but remained in action. The journal concluded that with regular equipment, the upgraded T-90 seems to be the best protected Russian tank, especially with the implementation of Shtora-1, the T-90A was deployed to Syria in 2015 to support the Russian involvement in the Syrian Civil War. In early February 2016, Syrian Army forces began using T-90As in combat, in late February, a video was leaked on the internet which showed a T-90 survive a direct frontal turret hit by a TOW-2A missile in Aleppo. The first alleged footage of the targeted tank showed only minor damage to Shtora-1 jammer optics, in early May there was another TOW attack scoring a hit on a different vehicle operated by Syrian loyalist forces

7.
PT-91 Twardy
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The PT-91 Twardy is a Polish main battle tank. A development of the T-72M1, it first entered service in 1995, the PT-91 was designed at the OBRUM and is produced by the Bumar Łabędy company, a part of the Bumar Group, a Polish technical military consortium. Changes from the T-72 include a new dual-axis stabilized fire-control system, reactive armour, many of those elements were used to upgrade existing fleets of T-72 tanks in countries including the Czech Republic, Georgia and India. In the late 1980s the Polish Army modernized all of its obsolete T-55 tanks to the T-55AM Mérida standard, the successful conversion convinced the General Staff that similar modernization could also be applied to other Soviet-designed tanks made in Poland and used by the Polish Armed Forces. In late 1988 it was decided to prepare a project of modernization for the T-72M1 design – using the experience from production of licensed T-72M, T-72M1, the Gliwice-based Research and Development Centre of Mechanical Systems OBRUM was chosen as the main design bureau. However, initially the work progressed at a slow pace. After the political changes of 1989 and the dissolution of the Soviet bloc, Polish-Soviet talks on purchase of modern tanks came to a halt, the first design proposed by the bureau was code-named Wilk, but the project was cancelled. Instead, the priority was shifted to a different project named Twardy, the basic aim of the conversion of T-72 was to adapt it to the reality of modern warfare and fix its most visible deficiencies. Among those were low mobility, insufficient armour, lack of a control system and poor stabilisation of the main gun. An additional problem was lack of night vision aiming systems. Starting from July 1991 T-72 modernization programs were implemented by the Bumarcombine which had been producing T-72s under Soviet license, the modernized main battle tank was designated PT-91 Twardy. From base modification it differs in increased protection, fire control system, in 1993 the Polish Defense Ministry ordered 20 PT-91 tanks to be used for field trials and Armed Forces tests. The main battle tanks protection from high-explosive anti-tank projectiles and missiles is increased by the new Erawa dynamic armor developed by the Poland Military-Technical Institute and this protection consists of 394 tiles with explosives, detonating in case of a direct hit. The tiles cover 9 m2 on the tank,108 tiles are placed on the turret,118 on the hull and 84 on each sides anti-HEAT screens. The Twardy uses steel anti-HEAT screens instead of the used on the T-72. Erawas main difference from the Soviet analogs is that Erawas containers fit almost without gaps while on the Soviet modernized T-72 gaps reach 10–15 mm noticeably decreasing defense effectiveness, there are two Erawa modifications, Erawa-1 and -2, differing in weight of the explosives. Experiments showed that the Erawa dynamic defense decreases the high-explosive jet impact depth by 50–70%, furthermore, explosive containers do not detonate when hit by shot of up to 30 mm calibre, shell or mine fragments, or when covered in burning napalm or petrol. Additional armament comprises the 7.62 mm PKT coaxial general-purpose machine gun and 12.7 mm NSVT anti-aircraft heavy machine gun, the PT-91 has a thermosmoke device generating smoke screens from fuel and 24 grenade launchers fitted with smoke or anti-personnel frag grenades

8.
T-14 Armata
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The T-14 Armata is a Russian main battle tank based on the Armata Universal Combat Platform. It is the first series-produced next generation tank, the Russian Army plans to acquire 2,300 T-14s in the period 2015–2020. It commenced testing in 2016 and production soon afterwards, featuring a number of innovative characteristics, the T-14 represents a new generation of Russian main battle tanks. The most significant new feature is the use of an unmanned turret, the development of the tank took five years. The main armament of the T-14 is the 2A82-1M125 mm smoothbore cannon, the detection range of the tanks optical sensors is more than 5 km for tank-sized targets in daylight, and at least 3.5 km at night through the thermal imaging channel. The gunner sights optical channel is equipped with 4× and 12× optical zoom, the laser rangefinder has a theoretical maximum range of 7.5 km. These systems are duplicated, in there is a weaker third system that can fire on the move. The crew uses a camera with a 360-degree field. The Vacuum-1 sabot round, developed for the 2A82-1M gun, has a penetrator that is 900 mm long, the new controlled-detonation Telnik HE-Frag shell is also available and has entered service. The gun is capable of firing guided missiles, a feature first implemented on 1960s Soviet tanks. These missiles can be used for air defense, the secondary armament consists of a 12.7 mm Kord machine gun with 300 rounds and a 7.62 mm PKTM machine gun with 1,000 rounds. In addition, another 1,000 rounds can be stored separately, in the future, the T-14 may use the 2A83152 mm gun instead of its current 2A82125 mm gun. This gun, created around 2000 for the T-95 prototype, has a high-speed APFSDS shell with a 1,980 m/s muzzle velocity, the T-14 can use anti-aircraft missiles. A30 mm anti-aircraft gun may be installed instead of the 12.7 machine gun, the T-14 is powered by a ChTZ 12Н360 diesel engine delivering up to 1,500 hp. Operational range is over 500 km, the T-14 has a 12-speed automatic gearbox, with a top speed of 80–90 kilometres per hour and a range of 500 kilometres. Other sources suggest a partly or fully hydrostatic transmission, uniquely for a Soviet/Russian design, the transmission is joined with the engine into a single unit that can be swapped out in the field in just under 30 minutes. Unlike previous Russian and Soviet designs, such as the T-90/80/72/64 and it has the ability to adjust the suspension of at least the two first roadwheels, and, probably, the last one. In the 2015 Moscow Victory Day Parade rehearsal video, a T-14 Armata is shown retracting one of its frontal first wheels during turns

9.
Sprut anti-tank gun
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2A45 and 2A45M are the respective GRAU designations of the Sprut-A and Sprut-B Soviet smoothbore 125 mm anti-tank gun. The 2A45M was created in the late 1980s by the Petrov Design Bureau at Artillery Plant Number 9, a feature of the Sprut-B is its integrated engine, which can propel the gun on relatively flat surfaces and at 14 km/h on roads. This gives the gun a measure of mobility on the battlefield and it takes two minutes to go from firing position to travelling position and 90 seconds to go from travelling position to firing position. Such guns are known in Russian as self-moving as opposed to self-propelled, the gun features a crew of seven. An OP4M-48A direct fire sight is used the day, while a 1PN53-1 night vision sight is used at night, for indirect fire, 2Ts33 iron sights are used, along with a PG-1m panoramic sight. The gun can engage targets two metres high at a distance of 2000 metres. The barrel features a thermal sleeve to prevent temperature changes affecting the accuracy, the gun uses the same semi-fixed ammunition as the T-64, T-72, T-80 and T-90 tanks. With the addition of the 9S53 laser fire-control system, the gun can fire laser guided projectiles such as the 9M119 Svir or 9K120 Refleks, the gun uses the same ammunition as the D-81 series of guns used on the T-64, T-72, T-80 and T-90 tanks. Sprut-SD 2S25 A self-propelled gun mounted on the BMD-3 chassis with a turret mounting the stabilised 2A75125 mm smoothbore gun, mexico Russia Ukraine, made under license, by KMDB, in the city of Kharkiv. Soviet Union passed construction license to successor states Belarus 125 mm smoothbore ammunition 2A46 - Soviet/Russian tank-mounted 125mm cannon List of Soviet tanks Hull, Soviet/Russian Armor and Artillery Design Practices 1945 to Present. Military Parade Enemy Forces 2A45M on manufacturer site Janes Armour and Artillery 2002-2003 Image

10.
Sabot
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Driving bands and obturator rings are made from material that will deform and seal the barrel as the projectile is forced from the chamber into the barrel. More detailed cutaways of the structural complexity of advanced APFSDS saboted long rod penetrator projectiles can be found at reference 2. Efficient aerodynamic design of a flight projectile does not always accommodate efficient interior ballistic design to high muzzle velocity. This is especially true for arrow-type projectiles, which are long and thin for low drag efficiency, the physics of interior ballistics demonstrates why the use of a sabot is advantageous to achieve higher muzzle velocity with an arrow-type projectile. Propellant gasses generate high pressure, and the larger the area that pressure acts upon the greater the net force on that surface. Force, pressure times area, provides an acceleration to the mass of the projectile, therefore, for a given pressure and barrel diameter, a lighter projectile can be driven from a barrel to a higher muzzle velocity than a heavier projectile. However, a projectile may not fit in the barrel. Upon muzzle exit, the sabot is discarded, and the flight projectile flies to the target with less drag resistance than a full-bore projectile. In this manner, very high velocity and slender, low drag projectiles can be fired more efficiently, nevertheless, the weight of the sabot represents parasitic mass that must also be accelerated to muzzle velocity, but does not contribute to the terminal ballistics of the flight projectile. The purpose of the sabot is to allow a smaller flight projectile to be launched at greater muzzle velocity than if the flight projectile alone were fired from a gun of equal caliber. Firing a smaller-sized projectile wrapped in a sabot raises the velocity of the projectile. The sabot usually consists of several longitudinal pieces held in place by the cartridge case, when the projectile is fired, the sabot blocks the gas, provides significant structural support against launch acceleration, and carries the projectile down the barrel. When the sabot reaches the end of the barrel, the shock of hitting still air pulls the parts of the sabot away from the projectile, sabot-type shotgun slugs were marketed in the United States starting in about 1985. When used with a rifled barrel, they offer vastly improved accuracy compared to traditional shotgun slugs. They are now legal for hunting in most U. S. states, a cup sabot supports the base and rear end of a projectile, and the cup material alone can provide both structural support and barrel obturation. When the sabot and projectile exit the muzzle of the gun, cup sabots are found typically in small arms ammunition, smooth-bore shotgun and smooth-bore muzzleloader projectiles. Used typically in rifled small arms, an expanding cup sabot has a one piece sabot surrounding the base and sides of a projectile, to achieve gyroscopic stability of longer bullets in smaller diameter requires faster rifling. Therefore, if a bullet requires at least 1 turn in 7 inch twist, in 5. 56mm, however, larger caliber commercial rifles generally dont need such fast twist rates,1,10 being a readily available standard in 7. 62mm

11.
Tracer ammunition
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Tracer ammunition are bullets or cannon caliber projectiles that are built with a small pyrotechnic charge in their base. Ignited by the powder, the pyrotechnic composition burns very brightly, making the projectile trajectory visible to the naked eye during daylight. This enables the shooter to make aiming corrections without observing the impact of the rounds fired, tracer fire can also be used to signal to other shooters where to concentrate their fire during battle. When used, tracers are usually loaded as every fifth round in machine gun belts, platoon and squad leaders will load some tracer rounds in their magazine or even use solely tracers to mark targets for their soldiers to fire on. Tracers are also placed two or three rounds from the bottom of magazines to alert the shooter that his weapon is almost empty. Unfortunately, this practice would similarly alert an astute enemy that his foe was nearly out of ammunition, more often, however, the entire magazine was loaded four-to-one, on both fixed offensive and flexible defensive guns, to help mitigate the difficulties of aerial gunnery. The United States relied heavily on tracer ammunition for the defensive Browning M2 and this proved true of fixed forward firing guns as well. Tracer rounds can also have an incendiary effect, and can ignite flammable substances on contact. Before the development of tracers, gunners relied on seeing their bullet impacts to adjust their aim, in the early 20th century, ammunition designers developed spotlight bullets, which would create a flash or smoke puff on impact to increase their visibility. However, these projectiles were deemed in violation of the Hague Conventions prohibition of exploding bullets and this strategy was also useless when firing at aircraft, as there was nothing for the projectiles to impact on if they missed the target. Designers also developed bullets that would trail white smoke, however, these designs required an excessive amount of mass loss to generate a satisfactory trail. The loss of mass en route to the severely affected the bullets ballistics. The United Kingdom was the first to develop and introduce a tracer round, the United States introduced a. 30-06 tracer in 1917. Prior to adopting red bullet tips for tracers, American tracers were identified by blackened cartridge cases, tracers proved useful as a countermeasure against Zeppelins used by Germany during World War I. The airships were used for reconnaissance, surveillance and bombing operations, normal bullets merely had the effect of causing a slow leak, but tracers could ignite the hydrogen gasbags, and bring down the airship quickly. In World War II US naval and marine aircrew were issued tracer rounds with their arms for emergency signaling use as well as defense. A tracer projectile is constructed with a base filled with a pyrotechnic flare material, made of a mixture of a very finely ground metallic fuel, oxidizer. Metallic fuels include magnesium, aluminum, and occasionally zirconium, the oxidizer is a salt molecule which contains oxygen combined with a specific atom responsible for the desired color output

12.
APFSDS
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Armour-piercing fin-stabilized discarding-sabot is a type of kinetic energy penetrator ammunition used to attack modern vehicle armour. As an armament for main battle tanks, it succeeds armour-piercing discarding sabot ammunition, when sloped dramatically backward adding obliquity and incorporating spaced armor, the line-of-sight thickness of armor arrays can increase to several feet, with limited armor weight increase. Armour-piercing discarding sabot was initially the main design of the kinetic energy penetrator, the logical progression was to make the shot longer and thinner to concentrate the kinetic energy in a smaller area. However, a long, thin rod is aerodynamically unstable, it tends to tumble in flight and is less accurate, traditionally, rounds were given stability in flight from the rifling of the gun barrel, which imparts a spin to the round. Up to a limit, this is effective, but once the projectiles length is more than six or seven times its diameter. Adding fins like the fletching of an arrow to the base gives the round stability, nevertheless, in the early development of APFSDS ammunition, existing rifled barrel cannons were used, such as the M68-105mm cannon mounted on the M60A3 main battle tank. The projectile still exits the barrel with some residual spinning, in addition, some spin rate is beneficial to a fin-stabilized projectile, averaging out aerodynamic imbalances and improving accuracy. These deep penetrating shaped charges also require fin stabilization, the concept of armor defeat using a long rod penetrator is a practical application of the phenomenon of hydro-dynamic penetration. One observes immediately that longer, denser penetrators will penetrate to depths. However, practical penetrator and target materials are not fluids, nevertheless, at sufficiently high impact velocity, even crystaline materials begin to behave in a highly plastic fluid-like manner, so many aspects of hydro-dynamic penetration do apply. S. Both materials are very dense, hard, tough and ductile, nevertheless, each material exhibits its own unique penetration qualities that may or may not be the best choice for any one anti-armor application. Additionally, DU penetrators exhibit significant adiabatic shear band formation, typical velocities of APFSDS rounds vary between manufacturers and muzzle length/types. As a typical example, the American General Dynamics KEW-A1 has a velocity of 1,740 m/s. This compares to 914 m/s for a rifle round. APFSDS rounds generally operate in the range of 1,400 to 1,900 m/s, often, however, the greater engineering challenge is designing an efficient sabot to successfully launch extremely long penetrators, now approaching 800 millimeters in length. The sabot, necessary to fill the bore of the cannon firing a long. For this reason, even in combat, tank gunners have to be aware of troop over-fire safety, the counterpart of APFSDS in rifle ammunition is the saboted flechette. A rifle firing flechettes, the Special Purpose Individual Weapon, was under development for the U. S. Army, compact Kinetic Energy Missile Impact depth Kinetic bombardment MGM-166 LOSAT

13.
Tank
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A tank is an armoured fighting vehicle designed for front-line combat, with heavy firepower, strong armour, and tracks providing good battlefield maneuverability. The first tanks were designed to overcome the deadlock of trench warfare, now they are a mainstay of ground forces. Modern tanks are versatile mobile land weapon platforms, mounting a large-calibre cannon in a rotating gun turret. In both offensive and defensive roles, they are units that are capable of performing tasks which are required of armoured units on the battlefield. As a result of advances, tanks underwent tremendous shifts in capability in the years since their first appearance. Tanks in World War I were developed separately and simultaneously by Great Britain and this was a prototype of a new design that would become the British Armys Mark I tank, the first tank used in combat in September 1916 during the Battle of the Somme. The name tank was adopted by the British during the stages of their development. While the British and French built thousands of tanks in World War I, Germany was unconvinced of the tanks potential, Tanks of the interwar period evolved into the much larger and more powerful designs of World War II. Tanks in the Cold War were designed with these weapons in mind, improved engines, transmissions and suspensions allowed tanks of this period to grow larger. Aspects of gun technology changed significantly as well, with advances in shell design, during the Cold War, the main battle tank concept arose and became a key component of modern armies. Modern tanks seldom operate alone, as they are organized into combined arms units which involve the support of infantry and they are also usually supported by reconnaissance or ground-attack aircraft. The tank is the 20th century realization of an ancient concept, the internal combustion engine, armour plate, and continuous track were key innovations leading to the invention of the modern tank. Many sources imply that Leonardo da Vinci and H. G. Wells in some way foresaw or invented the tank, leonardos late 15th century drawings of what some describe as a tank show a man-powered, wheeled vehicle with cannons all around it. However the human crew would not have power to move it over larger distance. In the 15th century, Jan Žižka built armoured wagons containing cannons, the caterpillar track arose from attempts to improve the mobility of wheeled vehicles by spreading their weight, reducing ground pressure, and increasing their traction. Experiments can be traced back as far as the 17th century and it is frequently claimed that Richard Lovell Edgeworth created a caterpillar track. It is true that in 1770 he patented a machine, that should carry and lay down its own road and his own account in his autobiography is of a horse-drawn wooden carriage on eight retractable legs, capable of lifting itself over high walls. The description bears no similarity to a caterpillar track, armoured trains appeared in the mid-19th century, and various armoured steam and petrol-engined vehicles were also proposed

14.
Maraging steel
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Maraging steels are steels that are known for possessing superior strength and toughness without losing malleability, although they cannot hold a good cutting edge. Aging refers to the extended heat-treatment process and these steels are a special class of low-carbon ultra-high-strength steels that derive their strength not from carbon, but from precipitation of intermetallic compounds. The principal alloying element is 15 to 25 wt. % nickel, secondary alloying elements, which include cobalt, molybdenum, and titanium, are added to produce intermetallic precipitates. Original development was carried out on 20 and 25 wt. % nickel, 8–12 wt. % cobalt, 3–5 wt. % molybdenum, addition of chromium produces stainless grades resistant to corrosion. Alternative variants of Ni-reduced maraging steels are based on alloys of Fe and Mn plus minor additions of Al, Ni, the Mn has a similar effect as Ni, i. e. it stabilizes the austenite phase. Hence, depending on their Mn content, Fe-Mn maraging steels can be fully martensitic after quenching them from the high temperature austenite phase or they can contain retained austenite, the latter effect enables the design of maraging-TRIP steels where TRIP stands for Transformation-Induced-Plasticity. Due to the low carbon content maraging steels have good machinability, prior to aging, they may also be cold rolled to as much as 90% without cracking. Maraging steels offer good weldability, but must be aged afterward to restore the properties to the heat affected zone. When heat-treated the alloy has very little change, so it is often machined to its final dimensions. Due to the alloy content maraging steels have a high hardenability. Since ductile FeNi martensites are formed upon cooling, cracks are non-existent or negligible, the steels can be nitrided to increase case hardness, and polished to a fine surface finish. Non-stainless varieties of maraging steel are moderately corrosion-resistant, and resist stress corrosion, corrosion-resistance can be increased by cadmium plating or phosphating. There is also a family of cobalt-free maraging steels which are cheaper but not quite as strong, there has been Russian and Japanese research in Fe-Ni-Mn maraging alloys. The steel is first annealed at approximately 820 °C for 15–30 minutes for thin sections and for 1 hour per 25 mm thickness for heavy sections and this is followed by air cooling to room temperature to form a soft, heavily-dislocated iron-nickel lath martensite. Overaging leads to a reduction in stability of the primary, metastable, coherent precipitates, leading to their dissolution, further excessive heat-treatment brings about the decomposition of the martensite and reversion to austenite. Maraging steels strength and malleability in the stage allows it to be formed into thinner rocket and missile skins than other steels. Maraging steels have very stable properties, and, even after overaging due to excessive temperature and these alloys retain their properties at mildly elevated operating temperatures and have maximum service temperatures of over 400 °C. They are suitable for engine components, such as crankshafts and gears, and their uniform expansion and easy machinability before aging make maraging steel useful in high-wear components of assembly lines and dies

15.
Soviet Union
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The Soviet Union, officially the Union of Soviet Socialist Republics was a socialist state in Eurasia that existed from 1922 to 1991. It was nominally a union of national republics, but its government. The Soviet Union had its roots in the October Revolution of 1917 and this established the Russian Socialist Federative Soviet Republic and started the Russian Civil War between the revolutionary Reds and the counter-revolutionary Whites. In 1922, the communists were victorious, forming the Soviet Union with the unification of the Russian, Transcaucasian, Ukrainian, following Lenins death in 1924, a collective leadership and a brief power struggle, Joseph Stalin came to power in the mid-1920s. Stalin suppressed all opposition to his rule, committed the state ideology to Marxism–Leninism. As a result, the country underwent a period of rapid industrialization and collectivization which laid the foundation for its victory in World War II and postwar dominance of Eastern Europe. Shortly before World War II, Stalin signed the Molotov–Ribbentrop Pact agreeing to non-aggression with Nazi Germany, in June 1941, the Germans invaded the Soviet Union, opening the largest and bloodiest theater of war in history. Soviet war casualties accounted for the highest proportion of the conflict in the effort of acquiring the upper hand over Axis forces at battles such as Stalingrad. Soviet forces eventually captured Berlin in 1945, the territory overtaken by the Red Army became satellite states of the Eastern Bloc. The Cold War emerged by 1947 as the Soviet bloc confronted the Western states that united in the North Atlantic Treaty Organization in 1949. Following Stalins death in 1953, a period of political and economic liberalization, known as de-Stalinization and Khrushchevs Thaw, the country developed rapidly, as millions of peasants were moved into industrialized cities. The USSR took a lead in the Space Race with Sputnik 1, the first ever satellite, and Vostok 1. In the 1970s, there was a brief détente of relations with the United States, the war drained economic resources and was matched by an escalation of American military aid to Mujahideen fighters. In the mid-1980s, the last Soviet leader, Mikhail Gorbachev, sought to reform and liberalize the economy through his policies of glasnost. The goal was to preserve the Communist Party while reversing the economic stagnation, the Cold War ended during his tenure, and in 1989 Soviet satellite countries in Eastern Europe overthrew their respective communist regimes. This led to the rise of strong nationalist and separatist movements inside the USSR as well, in August 1991, a coup détat was attempted by Communist Party hardliners. It failed, with Russian President Boris Yeltsin playing a role in facing down the coup. On 25 December 1991, Gorbachev resigned and the twelve constituent republics emerged from the dissolution of the Soviet Union as independent post-Soviet states

16.
Tungsten carbide
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Tungsten carbide is a chemical compound containing equal parts of tungsten and carbon atoms. Tungsten carbide is approximately two times stiffer than steel, with a Youngs modulus of approximately 530–700 GPa, and is double the density of steel—nearly midway between that of lead and gold. It is comparable with corundum in hardness and can only be polished and finished with abrasives of superior hardness such as boron nitride and diamond powder, wheels. Tungsten is Swedish for heavy stone, colloquially among workers in various industries, tungsten carbide is often simply called carbide, despite the inaccuracy of the usage. Among the lay public, the popularity of tungsten carbide rings has also led to consumers calling the material tungsten. Tungsten carbide is prepared by reaction of metal and carbon at 1400–2000 °C. Other methods include a lower temperature fluid bed process that reacts either tungsten metal or blue WO3 with CO/CO2 mixture. WC can also be produced by heating WO3 with graphite, both compounds may be present in coatings and the proportions can depend on the coating method. At high temperatures WC decomposes to tungsten and carbon and this can occur during high-temperature thermal spray, e. g. in high velocity oxygen fuel, oxidation of WC starts at 500–600 °C. It is resistant to acids and is attacked by hydrofluoric acid/nitric acid mixtures above room temperature. It reacts with fluorine gas at temperature and chlorine above 400 °C and is unreactive to dry H2 up to its melting point. Finely powdered WC oxidizes readily in hydrogen peroxide aqueous solutions, at high temperatures and pressures it reacts with aqueous sodium carbonate forming sodium tungstate, a procedure used for recovery of scrap cemented carbide.5 µm·m−1·K−1. Tungsten carbide is extremely hard, ranking about 9 on Mohs scale and it has a Youngs modulus of approximately 530–700 GPa, a bulk modulus of 630–655 GPa, and a shear modulus of 274 GPa. It has a tensile strength of 344 MPa, an ultimate compression strength of about 2.7 GPa. The speed of a wave through a thin rod of tungsten carbide is 6220 m/s. Tungsten carbides low electrical resistivity of about 0.2 µΩ·m is comparable with that of some metals, WC is readily wetted by both molten nickel and cobalt. Investigation of the diagram of the W-C-Co system shows that WC. There are two forms of WC, a form, α-WC, and a cubic high-temperature form, β-WC

17.
Depleted uranium
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Depleted uranium is uranium with a lower content of the fissile isotope U-235 than natural uranium. Natural uranium contains about 0. 72% U-235, while the DU used by the U. S. Department of Defense contains 0. 3% U-235 or less, uses of DU take advantage of its very high density of 19.1 g/cm3. In return, the radioactive and non-fissile uranium-238 constitutes the main component of depleted uranium. Civilian uses include counterweights in aircraft, radiation shielding in medical therapy and industrial radiography equipment. Military uses include armor plating and armor-piercing projectiles, most depleted uranium arises as a by-product of the production of enriched uranium for use as fuel in nuclear reactors and in the manufacture of nuclear weapons. Since U-238 has a much longer half-life than the lighter isotopes, DU from nuclear reprocessing has different isotopic ratios from enrichment–by-product DU, from which it can be distinguished by the presence of U-236. DU used in US munitions has 60% of the radioactivity of natural uranium, trace transuranics have been reported to be present in some US tank armor. The use of DU in munitions is controversial because of concerns about potential health effects. Normal functioning of the kidney, brain, liver, heart, and numerous other systems can be affected by exposure to uranium and it is only weakly radioactive because of its long radioactive half-life. The biological half-life for uranium is about 15 days, the actual level of acute and chronic toxicity of DU is also controversial. Several studies using cultured cells and laboratory rodents suggest the possibility of leukemogenic, genetic, reproductive, a 2005 epidemiology review concluded, In aggregate the human epidemiological evidence is consistent with increased risk of birth defects in offspring of persons exposed to DU. Enriched uranium was first manufactured in the early 1940s when the United States, later in the decade, France and the Soviet Union began their nuclear weapons and nuclear power programs. Depleted uranium was originally stored as a waste product in the hope that improved enrichment processes could extract additional quantities of the fissionable U-235 isotope. This re-enrichment recovery of the residual uranium-235 is now in practice in parts of the world. It is possible to design civilian power-generating reactors using unenriched fuel, thus most civilian reactors as well as all naval reactors and nuclear weapons production require fuel containing concentrated U-235 and generate depleted Uranium. In the 1970s, the Pentagon reported that the Soviet military had developed armor plating for Warsaw Pact tanks that NATO ammunition could not penetrate, the Pentagon began searching for material to make denser armor-piercing projectiles. After testing various metals, ordnance researchers settled on depleted uranium, the US and NATO militaries used DU penetrator rounds in the 1991 Gulf War, the Bosnia war, bombing of Serbia, the 2003 invasion of Iraq, and 2015 airstrikes on ISIS in Syria. It is estimated that between 315 and 350 tons of DU were used in the 1991 Gulf War, natural uranium metal contains about 0. 71% U-235,99. 28% U-238, and about 0. 0054% U-234

18.
Russia
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Russia, also officially the Russian Federation, is a country in Eurasia. The European western part of the country is more populated and urbanised than the eastern. Russias capital Moscow is one of the largest cities in the world, other urban centers include Saint Petersburg, Novosibirsk, Yekaterinburg, Nizhny Novgorod. Extending across the entirety of Northern Asia and much of Eastern Europe, Russia spans eleven time zones and incorporates a range of environments. It shares maritime borders with Japan by the Sea of Okhotsk, the East Slavs emerged as a recognizable group in Europe between the 3rd and 8th centuries AD. Founded and ruled by a Varangian warrior elite and their descendants, in 988 it adopted Orthodox Christianity from the Byzantine Empire, beginning the synthesis of Byzantine and Slavic cultures that defined Russian culture for the next millennium. Rus ultimately disintegrated into a number of states, most of the Rus lands were overrun by the Mongol invasion. The Soviet Union played a role in the Allied victory in World War II. The Soviet era saw some of the most significant technological achievements of the 20th century, including the worlds first human-made satellite and the launching of the first humans in space. By the end of 1990, the Soviet Union had the second largest economy, largest standing military in the world. It is governed as a federal semi-presidential republic, the Russian economy ranks as the twelfth largest by nominal GDP and sixth largest by purchasing power parity in 2015. Russias extensive mineral and energy resources are the largest such reserves in the world, making it one of the producers of oil. The country is one of the five recognized nuclear weapons states and possesses the largest stockpile of weapons of mass destruction, Russia is a great power as well as a regional power and has been characterised as a potential superpower. The name Russia is derived from Rus, a state populated mostly by the East Slavs. However, this name became more prominent in the later history, and the country typically was called by its inhabitants Русская Земля. In order to distinguish this state from other states derived from it, it is denoted as Kievan Rus by modern historiography, an old Latin version of the name Rus was Ruthenia, mostly applied to the western and southern regions of Rus that were adjacent to Catholic Europe. The current name of the country, Россия, comes from the Byzantine Greek designation of the Kievan Rus, the standard way to refer to citizens of Russia is Russians in English and rossiyane in Russian. There are two Russian words which are translated into English as Russians

19.
High-explosive anti-tank warhead
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High-explosive anti-tank warhead is a type of shaped charge explosive that uses the Munroe effect to penetrate armor. The warhead functions by having the explosive charge melt a metal liner to form a high-velocity superplastic jet and this concentrated metal jet is capable of penetrating armor steel to a depth of seven or more times the diameter of the charge. Contrary to a misconception, the jet does not melt its way through armor. The HEAT warhead has become less effective against tanks and other armored vehicles due to the use of composite armour, HEAT warheads were developed during World War II, from extensive research and development into shaped charge warheads. Shaped charge warheads were promoted internationally by the Swiss inventor Henry Mohaupt, before 1939, Mohaupt demonstrated his invention to British and French ordnance authorities. Claims for priority of invention are difficult to due to subsequent historic interpretations, secrecy, espionage. This has some claim to have been the first HEAT warhead, the design of the warhead was simple and was capable of penetrating 52 millimetres of armour. The fuze of the grenade was armed by removing a pin in the tail which prevented the firing pin from flying forward. Simple fins gave it stability in the air and, provided the hit the target at the proper angle of 90 degrees. Detonation occurred on impact, when a striker in the tail of the grenade overcame the resistance of a spring and was thrown forward into a stab detonator. By mid-1940, Germany introduced the first HEAT round to be fired by a gun, the 7.5 centimetres fired by the Kw. K.37 L/24 of the Panzer IV tank and the Stug III self-propelled gun. The Panzerfaust and Panzerschreck gave the German infantryman the ability to any tank on the battlefield from 50–150 metres with relative ease of use. The Germans made use of quantities of HEAT ammunition in converted 7.5 cm Pak 97/38 guns from 1942. These so-called Schwere Hohlladung warheads were intended for use against heavily armoured battleships, operational versions weighed nearly two tons and were perhaps the largest HEAT warheads ever deployed. A five-ton version code-named Beethoven was also developed, meanwhile, the British No.68 AT rifle grenade was proving to be too light to deal significant damage, resulting in it rarely being used in action. Due to these limits, a new infantry weapon was needed. By 1942, the PIAT had been developed by Major Millis Jefferis and it was a combination of a HEAT warhead with a spigot mortar delivery system. While cumbersome, the weapon allowed British infantry to armour at range for the first time

20.
Armoured personnel carrier
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An armoured personnel carrier is a type of armoured fighting vehicle designed to transport infantry to the battlefield. APCs are colloquially referred to as taxis or battle buses. Armoured personnel carriers are distinguished from infantry fighting vehicles by the weaponry they carry, by convention, they are not intended to take part in direct-fire battle, but are armed for self-defence and armoured to provide protection from shrapnel and small arms fire. Examples include the American M113, the French VAB, the Dutch-German GTK Boxer, the genesis of the armoured personnel carrier was on the Western Front of World War I. In the later stage of the war, Allied tanks could break through enemy lines, without infantry support, the tanks were isolated and more easily destroyed. In response, the British experimented with carrying machine-gun crews in the Mark V* tank, britain therefore designed the first purpose built armoured troop transport, the Mark IX, but the war ended before it could be put to use. During World War II, half-tracks like the American M3 and German SdKfz 251 played a similar to post-war APCs. British Commonwealth forces relied on the full-tracked Universal Carrier, over the course of the war, APCs evolved from simple armoured cars with transport capacity, to purpose built vehicles. Obsolete armoured vehicles were also repurposed as APCs, such as the various Kangaroos converted from M7 Priest self-propelled guns and from Churchill, M3 Stuart, during the Cold War, more specialized APCs were developed. Western nations have since retired most M113s, replacing them with newer APCs, the Soviet Union produced the BTR-40, BTR-152, BTR-60, BTR-70, BTR-80 in large numbers. The BTR-60 and BTR-80 remain in production, czechoslovakia and Poland together developed the universal amphibious OT-64 SKOT. A cold war example of a Kangaroo is the heavily armoured Israeli Achzarit, weight can vary from 6 to 40 tons or more, but 9 to 20 tons is typical. Most have a capacity of between 8 and 12 dismountable troops, although some can carry more than 20, in addition, it has a crew of at least one driver, many with a gunner and/or commander as well. An APC is either wheeled or tracked, or occasionally a combination of the two, as in a half-track, both systems have advantages and limitations. Tracked vehicles have more traction off-road and more maneuverability, including a turn radius. Wheeled APCs are faster on road, can cross long distances, and are expensive to develop, produce. However, wheeled vehicles have higher pressure than tracked vehicles with a comparable weight. The higher ground pressure increases the likelihood of becoming immobilized by soft terrains such as mud and their tracks can propel the APC in the water

21.
Milliradian
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A milliradian, often called a mil or mrad, is an SI derived unit for angular measurement which is defined as a thousandth of a radian. Mils are used in adjustment of firearm sights by adjusting the angle of the sight compared to the barrel, Mils are also used for comparing shot groupings, or to compare the difficulty of hitting different sized targets at different distances. Using optics with mil markings in the one can make a range estimation of a known size target, or vice versa to determine a target size if the distance is known. In such applications it is useful to use a unit for target size that is a thousandth of the unit for range, for instance by using the metric units millimeters for target size and meters for range. This coincides with the definition of the milliradian where the arc length is defined as 1/1000 of the radius, a common adjustment value in firearm sights is 1 cm at 100 meters which equals 10 mm/100 m = 1/10 mil. The true definition of a milliradian is based on a circle with a radius of one. There are other definitions used for mapping and artillery which are rounded to more easily be divided into smaller parts. The milliradian was first used in the mid nineteenth century by Charles-Marc Dapples, degrees and minutes were the usual units of angular measurement but others were being proposed, with grads under various names having considerable popularity in much of northern Europe. However, Imperial Russia used a different approach, dividing a circle into equilateral triangles, around the time of the start of World War I, France was experimenting with the use of milliemes for use with artillery sights instead of decigrades. The United Kingdom was also trialing them to replace degrees and minutes and they were adopted by France although decigrades also remained in use throughout World War I. The United States, which copied many French artillery practices, adopted mils, before 2007 the Swedish defence forces used streck which is closer to the milliradian but then changed to NATO mils. After the Bolshevik Revolution and the adoption of the system of measurement the Red Army expanded the 600 unit circle into a 6000 mil one. Hence the Russian mil has a different origin than those derived from French artillery practices. In the 1950s, NATO adopted metric units of measurement for land, Mils, meters, and kilograms became standard, although degrees remained in use for naval and air purposes, reflecting civil practices. The approximation error by using the linear formula will increase as the angle increases. New shooters are often explained the principle of subtensions in order to understand that a milliradian is an angular measurement, subtension is the physical amount of space covered by an angle and varies with distance. Thus, the corresponding to a mil varies with range. Subtensions always change with distance, but a mil is always a mil regardless of distance, therefore ballistic tables and shot corrections are given in mils thereby avoiding the need of mathematical calculations

22.
RDX
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RDX is the organic compound with the formula 3. It is a white solid used as an explosive. Chemically, it is classified as nitramide, a more powerful explosive than TNT, it was used widely in World War II. It is often used in mixtures with other explosives and plasticizers or phlegmatizers, RDX is stable in storage and is considered one of the most powerful and brisant of the military high explosives. RDX is also known, but less commonly, as cyclonite, hexogen, T4, in the 1930s, the Royal Arsenal, Woolwich, started investigating cyclonite to use against German U-boats that were being built with thicker hulls. The goal was a more powerful than TNT. For security reasons, Britain termed cyclonite as Research Department Explosive, the term RDX appeared in the United States in 1946. The first public reference in the United Kingdom to the name RDX, RDX was widely used during World War II, often in explosive mixtures with TNT such as Torpex, Composition B, Cyclotols, and H6. RDX was used in one of the first plastic explosives, the bouncing bomb depth charges used in the Dambusters Raid each contained 6,600 pounds of Torpex. RDX is believed to have used in many bomb plots including terrorist plots. RDX forms the base for a number of military explosives, Composition A, Granular explosive consisting of RDX. C-4 consists of RDX, a plasticizer, a binder, which is usually polyisobutylene, Composition CH-6,97. 5% RDX,1. 5% calcium stearate,0. 5% polyisobutylene, and 0. 5% graphite. DBX, Castable mixture consisting of 21% RDX, 21% ammonium nitrate, 40% TNT, developed during World War II, it was to be used in underwater munitions as a substitute for Torpex employing only half the amount of then-strategic RDX. As the supply of RDX became more adequate, the mixture was shelved, Cyclotol, Castable mixture of RDX with TNT designated by the amount of RDX/TNT, such as Cyclotol 70/30. HBX, Castable mixtures of RDX, TNT, powdered aluminium, h-6, Castable mixture of RDX, TNT, powdered aluminum, and paraffin wax. PBX, RDX is also used as a component of many polymer-bonded explosives. RDX-based PBXs typically consist of RDX and a polymer/co-polymer binder, semtex, Plastic demolition explosives containing RDX and PETN as major energetic components. Torpex, 42% RDX, 40% TNT, and 18% powdered aluminium, the mixture was designed during World War II and used mainly in underwater ordnance

23.
Phlegmatized explosive
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Phlegmatized is a term applied to an explosive that has had an agent added to stabilize or desensitize it. Sometimes this is either to improve the handling properties of an explosive or to reduce its sensitivity. TNT explosive can itself be used to more sensitive explosives such as RDX. Other typical phlegmatizing agents include paraffin wax, paper or even water, such agents are nearly always flammable themselves or will at least boil off easily. Another example of use is the VS-50 antipersonnel mine, which contains a filling of 43 grams of RDX. Explosive compounds may exist in material states that limit their application, for instance, nitroglycerin is normally an oily liquid. Phlegmatization of nitroglycerin allows it to be formed as a solid and it also allows the liquid, which is very sensitive to shock, to be handled more vigorously

24.
HMX
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HMX, also called octogen, is a powerful and relatively insensitive nitroamine high explosive, chemically related to RDX. The molecular structure of HMX consists of a ring of alternating carbon and nitrogen atoms. Because of its molecular weight, it is one of the most potent chemical explosives manufactured, although a number of newer ones, including HNIW. HMX is more complicated to manufacture than most explosives and this confines it to specialist applications and it may be produced by nitration of hexamine in the presence of acetic anhydride, paraformaldehyde and ammonium nitrate. RDX produced using the Bachmann Process usually contains 8–10% HMX, also known as cyclotetramethylene-tetranitramine, tetrahexamine tetranitramine, or octahydro-1,3,5, 7-tetranitro-1,3,5, 7-tetrazocine, HMX was first made in 1930. In 1949 it was discovered that HMX can be prepared by nitrolysis of RDX, nitrolysis of RDX is performed by dissolving RDX in a 55% HNO3 solution, followed by placing the solution on a steambath for about six hours. HMX is used almost exclusively in military applications, including as the detonator in nuclear weapons, in the form of polymer-bonded explosive, HMX is used in melt-castable explosives when mixed with TNT, which as a class are referred to as octols. Additionally, polymer-bonded explosive compositions containing HMX are used in the manufacture of missile warheads, HMX is also used in the process of perforating the steel casing in oil and gas wells. The HMX is built into a charge that is detonated within the wellbore to punch a hole through the steel casing and surrounding cement out into the hydrocarbon bearing formations. The pathway that is created allows formation fluids to flow into the wellbore, the Hayabusa 2 space probe will use HMX to excavate a hole in an asteroid in order to access material that has not been exposed to the solar wind. At present, the information needed to determine if HMX causes cancer is insufficient, due to the lack of information, EPA has determined that HMX is not classifiable as to its human carcinogenicity. The available data on the effects on health of exposure to HMX are limited. HMX causes CNS effects similar to those of RDX, but at higher doses. In one study, volunteers submitted to testing, which produced skin irritation. Another study of a cohort of 93 workers at a plant found no hematological, hepatic, autoimmune. However, the study did not quantify the levels of exposure to HMX, HMX exposure has been investigated in several studies on animals. Overall, the toxicity appears to be quite low, HMX is poorly absorbed by ingestion. When applied to the dermis, it induces mild skin irritation, various acute and subchronic neurobehavioral effects have been reported in rabbits and rodents, including ataxia, sedation, hyperkinesia, and convulsions

25.
TNT
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Trinitrotoluene, or more specifically 2,4, 6-trinitrotoluene, is a chemical compound with the formula C6H23CH3. This yellow-colored solid is used as a reagent in chemical synthesis. The explosive yield of TNT is considered to be the measure of bombs. In chemistry, TNT is used to charge transfer salts. TNT was first prepared in 1863 by German chemist Julius Wilbrand and its potential as an explosive was not appreciated for several years, mainly because it was so difficult to detonate and because it was less powerful than alternatives. Its explosive properties were first discovered by another German chemist, Carl Häussermann, the German armed forces adopted it as a filling for artillery shells in 1902. The British started replacing lyddite with TNT in 1907, TNT is still widely used by the United States military, as well as construction companies around the world. The majority of TNT currently used by the US military is manufactured by Radford Army Ammunition Plant near Radford, in industry, TNT is produced in a three-step process. First, toluene is nitrated with a mixture of sulfuric and nitric acid to produce mononitrotoluene, the MNT is separated and then renitrated to dinitrotoluene. In the final step, the DNT is nitrated to trinitrotoluene using a mixture of nitric acid. Nitric acid is consumed by the process, but the diluted sulfuric acid can be reconcentrated and reused. The rinse water from sulphitation is known as red water and is a significant pollutant, control of nitrogen oxides in feed nitric acid is very important because free nitrogen dioxide can result in oxidation of the methyl group of toluene. This reaction is exothermic and carries with it the risk of a runaway reaction leading to an explosion. In the laboratory,2,4, 6-trinitrotoluene is produced by a two-step process, a nitrating mixture of concentrated nitric and sulfuric acids is used to nitrate toluene to a mixture of mono- and di-nitrotoluene isomers, with careful cooling to maintain temperature. The nitrated toluenes are then separated, washed with dilute sodium bicarbonate to remove oxides of nitrogen, towards the end of the nitration, the mixture is heated on a steam bath. The trinitrotoluene is separated, washed with a solution of sodium sulfite. TNT is one of the most commonly used explosives for military, industrial, TNT has been used in conjunction with hydraulic fracturing, a process used to recover oil and gas from shale formations. The technique involves displacing and detonating nitroglycerin in hydraulically induced fractures followed by wellbore shots using pelletized TNT, TNT is valued partly because of its insensitivity to shock and friction, with reduced risk of accidental detonation compared to more sensitive explosives such as nitroglycerin

26.
Chobham armour
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Chobham armour is the informal name of a composite armour developed in the 1960s at the British tank research centre on Chobham Common, Surrey. The name has become the common generic term for composite ceramic vehicle armour. Other names informally given to Chobham Armour include Burlington and Dorchester, due to the extreme hardness of the ceramics used, they offer superior resistance against shaped charges such as high explosive anti-tank rounds and they shatter kinetic energy penetrators. The armour was first tested in the context of the development of a British prototype vehicle, the FV4211, only the M1 Abrams, Challenger 1, and Challenger 2 tanks have been disclosed as being thus armoured. The framework holding the ceramics is produced in large blocks, giving these tanks, and especially their turrets. Due to the hardness of the ceramics used, they offer superior resistance against a shaped charge jet. The ceramic also strongly abrades any penetrator and this initiates a vicious circle as the disturbed jet causes still greater irregularities in the ceramic, until in the end it is defeated. The newer composites, though tougher, optimise this effect as tiles made with them have an internal structure conducive to it. This mechanism—using the jets own energy against it—has caused the effects of Chobham to be compared to those of reactive armour. This should not be confused with the used in many laminate armours of any kind. Both attack methods will suffer from obstruction to their expected paths, so experiencing a greater thickness of armour than there is nominally, thus lowering penetration. Also for rod penetrations, the force experienced due to the deformation may cause the rod to shatter, bend, or just change its path. During the second Iraq war in 2003, a Challenger 2 tank became stuck in a ditch while fighting in Basra against Iraqi forces, the crew remained safe inside for many hours, the composite Chobham 2 armour protecting them from enemy fire, including rocket propelled grenades. Ceramic tiles have a multiple hit capability problem in that they cannot sustain successive impacts without quickly losing much of their protective value. The small hexagonal or square ceramic tiles are encased within the matrix either by pressing them into the heated matrix. The matrix has to be backed by a plate, both to reinforce the ceramic tiles from behind and to prevent deformation of the matrix by a kinetic impact. Typically the backing plate has half of the mass of the composite matrix, the assemblage is again attached to elastic layers. These absorb impacts somewhat, but their function is to prolong the service life of the composite matrix by protecting it against vibrations

27.
Explosive material
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An explosive charge is a measured quantity of explosive material, which may be composed of a single ingredient or a combination of two or more. Materials that detonate are said to be high explosives and materials that deflagrate are said to be low explosives, Explosives may also be categorized by their sensitivity. Sensitive materials that can be initiated by a small amount of heat or pressure are primary explosives. A wide variety of chemicals can explode, a number are manufactured specifically for the purpose of being used as explosives. The remainder are too dangerous, sensitive, toxic, expensive, unstable, in contrast, some materials are merely combustible or flammable if they burn without exploding. The distinction, however, is not razor-sharp, though early thermal weapons, such as Greek fire, have existed since ancient times, the first widely used explosive in warfare and mining was black powder, invented in 9th century China. This material was sensitive to water, and it produced copious amounts of dark smoke, the first useful explosive stronger than black powder was nitroglycerin, developed in 1847. Since nitroglycerin is a liquid and highly unstable, it was replaced by nitrocellulose, TNT in 1863, smokeless powder, dynamite in 1867, World War I saw the adoption of TNT trinitrotoluene in artillery shells. World War II saw a use of new explosives. In turn, these have largely replaced by more powerful explosives such as C-4. However, C-4 and PETN react with metal and catch fire easily, yet unlike TNT, C-4 and PETN are waterproof, the largest commercial application of explosives is mining. In Materials Science and Engineering, explosives are used in cladding, a thin plate of some material is placed atop a thick layer of a different material, both layers typically of metal. Atop the thin layer is placed an explosive, at one end of the layer of explosive, the explosion is initiated. The two metallic layers are forced together at high speed and with great force, the explosion spreads from the initiation site throughout the explosive. Ideally, this produces a metallurgical bond between the two layers and it is possible that some fraction of the surface material from either layer eventually gets ejected when the end of material is reached. Hence, the mass of the now welded bilayer, may be less than the sum of the masses of the two initial layers, there are applications where a shock wave, and electrostatics, can result in high velocity projectiles. Thus, explosives are substances that contain an amount of energy stored in chemical bonds. Consequently, most commercial explosives are compounds containing -NO2, -ONO2 and -NHNO2 groups that

28.
Bunker
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A bunker is a defensive military fortification designed to protect people or valued materials from falling bombs or other attacks. Bunkers are mostly underground, compared to blockhouses which are mostly above ground and they were used extensively in World War I, World War II, and the Cold War for weapons facilities, command and control centers, and storage facilities. Bunkers can also be used as protection from tornadoes, trench bunkers are small concrete structures, partly dug into the ground. Many artillery installations, especially for coastal artillery, have historically been protected by extensive bunker systems, typical industrial bunkers include mining sites, food storage areas, dumps for materials, data storage, and sometimes living quarters. When a house is purpose-built with a bunker, the location is a reinforced below-ground bathroom with fibre-reinforced plastic shells. Bunkers deflect the blast wave from nearby explosions to prevent ear, nuclear bunkers must also cope with the underpressure that lasts for several seconds after the shock wave passes, and block radiation. A bunkers door must be at least as strong as the walls, in bunkers inhabited for prolonged periods, large amounts of ventilation or air conditioning must be provided. Bunkers can be destroyed with explosives and bunker-busting warheads. The word bunker originates as a Scots word for bench, seat, the word possibly has a Scandinavian origin, Old Swedish bunke means boards used to protect the cargo of a ship. A sense of earthen seat is recorded 1805, with the spelling boncure from whence the use to refer to sand traps in golf, all the early references to its usage in the Oxford English Dictionary are to German fortifications. This type of bunker is a concrete structure, partly dug into the ground. Such bunkers give the defending soldiers better protection than the open trench and they also provide shelter against the weather. The front bunker of a system usually includes machine guns or mortars. The rear bunkers are usually used as posts or Tactical Operations Centers, for storage. Many artillery installations, especially for coastal artillery, have historically been protected by extensive bunker systems, artillery bunkers are some of the largest individual pre-Cold War bunkers. The walls of the Batterie Todt gun installation in northern France were up to 3.5 m thick, typical industrial bunkers include mining sites, food storage areas, dumps for materials, data storage, and sometimes living quarters. They were built mainly by nations like Germany during World War II to protect important industries from aerial bombardment, industrial bunkers are also built for control rooms of dangerous activities, e. g. tests of rocket engines or explosive experiments. They are also built in order to perform experiments in them or to store radioactive or explosive goods

29.
Aluminium
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Aluminium or aluminum is a chemical element in the boron group with symbol Al and atomic number 13. It is a silvery-white, soft, nonmagnetic, ductile metal, Aluminium metal is so chemically reactive that native specimens are rare and limited to extreme reducing environments. Instead, it is combined in over 270 different minerals. The chief ore of aluminium is bauxite, Aluminium is remarkable for the metals low density and its ability to resist corrosion through the phenomenon of passivation. Aluminium and its alloys are vital to the industry and important in transportation and structures, such as building facades. The oxides and sulfates are the most useful compounds of aluminium, despite its prevalence in the environment, no known form of life uses aluminium salts metabolically, but aluminium is well tolerated by plants and animals. Because of these salts abundance, the potential for a role for them is of continuing interest. Aluminium is a soft, durable, lightweight, ductile. It is nonmagnetic and does not easily ignite, a fresh film of aluminium serves as a good reflector of visible light and an excellent reflector of medium and far infrared radiation. The yield strength of aluminium is 7–11 MPa, while aluminium alloys have yield strengths ranging from 200 MPa to 600 MPa. Aluminium has about one-third the density and stiffness of steel and it is easily machined, cast, drawn and extruded. Aluminium atoms are arranged in a cubic structure. Aluminium has an energy of approximately 200 mJ/m2. Aluminium is a thermal and electrical conductor, having 59% the conductivity of copper. Aluminium is capable of superconductivity, with a critical temperature of 1.2 kelvin. Aluminium is the most common material for the fabrication of superconducting qubits, the strongest aluminium alloys are less corrosion resistant due to galvanic reactions with alloyed copper. This corrosion resistance is reduced by aqueous salts, particularly in the presence of dissimilar metals. In highly acidic solutions, aluminium reacts with water to form hydrogen, primarily because it is corroded by dissolved chlorides, such as common sodium chloride, household plumbing is never made from aluminium

30.
Attack helicopter
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An attack helicopter is an armed helicopter with the primary role of an attack aircraft, with the capability of engaging targets on the ground, such as enemy infantry and armored fighting vehicles. Due to their heavy armament they are sometimes called helicopter gunships, weapons used on attack helicopters can include autocannons, machine guns, rockets, and guided anti-tank missiles such as the Hellfire. Many attack helicopters are capable of carrying air-to-air missiles, though mostly for purposes of self-defense. Todays attack helicopter has two roles, first, to provide direct and accurate close air support for ground troops. Attack helicopters are used to supplement lighter helicopters in the armed scout role. In combat, a helicopter is projected to destroy around 17 times its own production cost before it is destroyed. S. Army artillery spotter units over France, these aircraft were field-outfitted with either two or four bazooka rocket launchers attached to the struts, against German armored fighting vehicles. During the summer of 1944, U. S. Army Major Charles Carpenter managed to take on an anti-armor role with his rocket-armed Piper L-4. The only American helicopter in use during the war years, the Sikorsky R-4, was only being used for rescue and were very much experimental in nature. In the early 1950s, various countries around the world started to make increased use of helicopters in their operations in transport and liaison roles. Later on it was realised that these helicopters, successors to the World War II-era Sikorsky R-4, early examples include armed Sikorsky H-34s in service with the US Air Force and armed Mil Mi-4 in service with the Soviet Air Forces. This trend continued into the 1960s with the deployment of armed Bell UH-1s and Mil Mi-8s during the Vietnam War, by the 1990s, the missile-armed attack helicopter evolved into a primary anti-tank weapon. Able to quickly move about the battlefield and launch fleeting pop-up attacks, the helicopter gunship became a major tool against tank warfare, and most attack helicopters became more and more optimized for the antitank mission. Based on this realization, and with the involvement in Vietnam, the U. S. Army developed the requirements for a dedicated attack helicopter. The aircraft design selected for this program in 1965, was Lockheeds AH-56 Cheyenne, as the Army began its acquisition of a dedicated attack helicopter, it sought options to improve performance over the continued use of improvised interim aircraft. The three highest-ranked aircraft, the Sikorsky S-61, Kaman H-2 Tomahawk, and the Bell AH-1 Cobra, were selected to compete in trials conducted by the Armys Aviation Test Activity. Upon completion of the evaluations, the Test Activity recommended Bells Huey Cobra to be an interim armed helicopter until the Cheyenne was fielded. On 13 April 1966, the U. S. Army awarded Bell Helicopter Company a production contract for 110 AH-1G Cobras, the Cobra had a tandem cockpit seating arrangement to make the aircraft a smaller frontal target, increased armor protection, and greater speed

31.
9K112 Kobra
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The 9K112 Kobra is a SACLOS anti-tank missile system of the Soviet Union. It is fired from the 125 mm main guns of the T-64, a newer design based on the same concept is the 9M119. The first generation of Soviet missile tanks started in 1956 when V. A, malyshev was ordered by Nikita Khrushchev to instill a new thinking into the weapons design bureaus. Part of this new thinking was the development of tanks, including the IT-1 firing the Drakon missile. However, these early designs were failures. A purely missile armed tank had a 300-meter deadzone around it, hybrid designs compromised both main gun firepower and missile carrying capacity. These limitations led to the development of a system, where the missile was fired through the barrel of the tanks main cannon. The first generation of concept was the Obiekt 775 tank, armed with a 125 mm smoothbore gun that could fire high explosive unguided rockets. The guided projectile was called Rubin and the unguided projectile called Bur, the tank could carry 24 Rubin missiles and 48 Bur rockets. The project was a failure, as the Rubins shaped charge warhead was not effective enough, but it was not until the 1970s that serious attention was paid to the concept again. This was probably because of three factors, The United States development of a 152 mm gun system for the M551 Sheridan. The development NATO anti-tank missiles such as TOW and Euromissile HOT systems, the increased threat of helicopters such as the AH-1 Cobra. Missiles could offer a degree of protection against treetop-hovering helicopters, the development of a second generation of Soviet tube fired guided projectiles began in the 1970s. The Kobra missile system was in competition with the IR guided Gyurza system, the IR guidance system of the Gyurza missile proved troublesome and the Kobra was put into production. The 9K112 was first mounted on a new version of the T-64B in 1976, the later T-80B in 1978 was also armed with the system. The Gyurza system continued to be developed, dropping the IR guidance system in favour of radio command guidance - it was developed into the Shturm or AT-6 Spiral. The 9M112 Kobra missile consists of two sections, 9M43 head section – containing the 9M129 shaped charge warhead and the 9D129 sustainer motor. 9B447 tail section – containing a battery, the controls, a light source for the guidance system on the tank to track

32.
9M119 Svir/Refleks
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The 9M119 Svir and 9M119M Refleks are laser beam riding, guided anti-tank missiles developed in the former Soviet Union. The two missiles are similar, but vary in range and launch platform, both are designed to be fired from smooth bore 125 mm tank and anti-tank guns. Their NATO reporting name is AT-11 Sniper, the name Svir comes from the River Svir, while Refleks means reflex. The 9M119 replaces, or supplants, the 9K112 Kobra, the Refleks is used in the T-90 and Serbian M-84AS and some versions of the T-80 and T-84 tanks. It has also produced by the Peoples Republic of China for use with its Type 98 tank. BDL has been manufacturing these missiles under technical collaboration with Rosoboronexport and it can also be fired from the 2A45 Sprut-B anti-tank gun. The Invar 9M119M and Invar 9M119M1 are fired from a 125mm gun, like a shell, the 17.2 kg missile is 690mm long and has pop-out fins that aid in guidance. The missile has a max range of 5,000 meters at a speed of 350 meters per second, the Invar enables the tank to hit targets at twice the range of the 125mm shells. The tandem warhead can penetrate up to 900mm of armor, missile 9M119M Invar put into service in 1992, and the missile 9M119M1 Invar-M in the second half of the 1990s. 9M119F and 9M119F1 guided missiles of high explosive action intended for defeat of enemy personnel, the Svir is used with the T-72 series of tanks. United States, MGM-51 Shillelagh used with the M551 Sheridan light tank, united States, XM1111 Mid-Range Munition which was attempted to be developed for the M1A2 SEP Abrams MBT. Russia, 9K112 Kobra is also fired through 125-mm smoothbore gun tubes, israel, LAHAT, used with their 105 and 120-mm gun tubes. France, ACRA 142mm anti-tank guided weapon, tested on a version of the AMX-30 MBT, ukraine, Kombat tandem-warhead ATGM with a 5, 000-m effective range, fired from 125-mm smoothbore guns. Iran, Reversed engineered version of the Svir with max range of 4,000 meters named Tondar

33.
Extremely high frequency
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Extremely high frequency is the International Telecommunications Union designation for the band of radio frequencies in the electromagnetic spectrum from 30 to 300 gigahertz. It lies between the high frequency band, and the far infrared band which is also referred to as the terahertz gap. Radio waves in this band have wavelengths from ten to one millimetre, giving it the name millimetre band or millimetre wave, millimetre-length electromagnetic waves were first investigated in the 1890s by Indian scientist Jagadish Chandra Bose. Compared to lower bands, radio waves in this band have high atmospheric attenuation, therefore, they have a short range and can only be used for terrestrial communication over about a kilometer. Absorption by humidity in the atmosphere is significant except in desert environments, however the short propagation range allows smaller frequency reuse distances than lower frequencies. The short wavelength allows modest size antennas to have a beam width. Millimeter waves propagate solely by line-of-sight paths, they are not reflected by the ionosphere nor do they travel along the Earth as ground waves as lower frequency radio waves do, at typical power densities they are blocked by building walls and suffer significant attenuation passing through foliage. The high free space loss and atmospheric absorption limits useful propagation to a few kilometers, thus they are useful for densely packed communications networks such as personal area networks that improve spectrum utilization through frequency reuse. They show optical propagation characteristics and can be reflected and focused by small metal surfaces around 1 ft. diameter, at millimeter wavelengths, surfaces appear rougher so diffuse reflection increases. Multipath propagation, particularly reflection from indoor walls and surfaces, causes serious fading, doppler shift of frequency can be significant even at pedestrian speeds. In portable devices, shadowing due to the body is a problem. Since the waves penetrate clothing and their small wavelength allows them to reflect from small metal objects they are used in millimeter wave scanners for security scanning. This band is used in radio astronomy and remote sensing. Ground-based radio astronomy is limited to high altitude such as Kitt Peak. Satellite-based remote sensing near 60 GHz can determine temperature in the atmosphere by measuring radiation emitted from oxygen molecules that is a function of temperature and pressure. The ITU non-exclusive passive frequency allocation at 57-59 and it is used commonly in flat terrain. The 71-76, 81-86 and 92–95 GHz bands are used for point-to-point high-bandwidth communication links. These higher frequencies do not suffer from oxygen absorption, but require a license in the US from the Federal Communications Commission

34.
Reactive armour
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Reactive armour is a type of vehicle armour that reacts in some way to the impact of a weapon to reduce the damage done to the vehicle being protected. It is most effective in protecting against shaped charges and specially hardened kinetic energy penetrators, NERA and NxRA modules can withstand multiple hits, unlike ERA and SLERA, but a second hit in exactly the same location will still penetrate any of those. Essentially all anti-tank munitions work by piercing the armour and killing the crew inside, disabling vital mechanical systems, reactive armour can be defeated with multiple hits in the same place, as by tandem-charge weapons, which fire two or more shaped charges in rapid succession. Without tandem charges, hitting the same spot twice is much more difficult, the idea of counterexplosion in armour was first proposed by the Scientific Research Institute of Steel in 1949 in the USSR by academician Bogdan Vjacheslavovich Voitsekhovsky. The first pre-production models were produced during the 1960s, however, insufficient theoretical analysis during one of the tests resulted in all of the prototype elements being blown up. For a number of reasons, including the accident, as well as a belief that Soviet tanks had sufficient armour, no more research was conducted until 1974 when the Ministry of the Defensive Industry announced a contest to find the best tank protection project. A West German researcher, Manfred Held carried out work with the IDF in 1967–69. Reactive armour created on the basis of the joint research was first installed on Israeli tanks during the 1982 Lebanon war and was judged very effective. An element of explosive reactive armour consists of a sheet or slab of high explosive sandwiched between two plates, typically metal, called the reactive or dynamic elements, on attack by a penetrating weapon, the explosive detonates, forcibly driving the metal plates apart to damage the penetrator. Against a shaped charge, the projected plates disrupt the metallic jet penetrator, against a kinetic energy penetrator, the projected plates serve to deflect and break up the rod. The disruption is attributed to two mechanisms and this second effect significantly increases the effective plate thickness during the impact. To be effective against kinetic energy projectiles, ERA must use much thicker and heavier plates, such heavy ERA, such as the Soviet-developed Kontakt-5, can break apart a penetrating rod that is longer than the ERA is deep, again significantly reducing penetration capability. An important aspect of ERA is the brisance, or detonation speed of its explosive element, a more brisant explosive and greater plate velocity will result in more plate material being fed into the path of the oncoming jet, greatly increasing the plates effective thickness. This effect is pronounced in the rear plate receding away from the jet. ERA also counters explosively forged projectiles, as produced by a shaped charge, the counter-explosion must disrupt the incoming projectile so that its momentum is distributed in all directions rather than towards the target, greatly diminishing its effectiveness. The U. S. Army uses reactive armour on its Abrams tanks as part of the TUSK package and on Bradley vehicles and the Israelis use it frequently on their American built M60 tanks. ERA tiles are used as add-on armour to the portions of a fighting vehicle that are most likely to be hit, typically the front of the hull. Their use requires that a vehicle be fairly heavily armoured to protect itself, the explosion of an ERA plate creates a significant amount of shrapnel, and bystanders are in grave danger of fatal injury

The T-80 is a third-generation main battle tank (MBT) designed and manufactured in the Soviet Union. When it entered …

Image: T 80U main battle tank

This T-80BV has reactive armour adapted to its turret and hull. The later T-80U has a large applique of explosive reactive armour installed — providing higher crew and tank survivability than prior models.

Extremely high frequency (EHF) is the International Telecommunication Union (ITU) designation for the band of radio …

Atmospheric attenuation in dB/km as a function of frequency over the EHF band. Peaks in absorption at specific frequencies are a problem, due to atmosphere constituents such as water vapour (H2O) and molecular oxygen (O2). The vertical scale is exponential.

RDX is the organic compound with the formula (O2NNCH2)3. It is a white solid widely used as an explosive. Chemically, …

RDX crystal

Preparing to load 1,000-lb MC bombs into the bomb-bay of an Avro Lancaster B Mark III of No. 106 Squadron RAF at RAF Metheringham, prior to a major night raid on Frankfurt. The stencilled lettering around the circumference of each bomb reads "RDX/TNT"